This invention relates to the fabrication of three-dimensional objects using additive process modeling techniques. More particularly, the invention relates to forming three-dimensional objects by depositing a first solidifiable material in a predetermined pattern so as to form a three-dimensional object, in coordination with the depositing of a second solidifiable material so as to provide a support structure for the three-dimensional object as it is being built.
Additive process modeling machines make three-dimensional models by building up a modeling medium, based upon design data provided from a computer aided design (CAD) system. Three-dimensional models are used for functions including aesthetic judgments, proofing the mathematical CAD model, forming hard tooling, studying interference and space allocation, and testing functionality. One technique is to deposit solidifiable modeling material in a predetermined pattern, according to design data provided from a CAD system, with the build-up of multiple layers forming the model.
Examples of apparatus and methods for making three-dimensional models by depositing layers of solidifiable modeling material from an extrusion head are described in Valavaara, U.S. Pat. No. 4,749,347; Crump, U.S. Pat. No. 5,121,329; Batchelder et al., U.S. Pat. No. 5,303,141; Crump, U.S. Pat. No. 5,340,433; Batchelder et al., U.S. Pat. No. 5,402,351; Crump et al., U.S. Pat. No. 5,503,785; Batchelder et al., U.S. Pat. No. 5,764,521; Danforth et al., U.S. Pat. No. 5,900,207; Batchelder et al., U.S. Pat. No. 5,968,561; Stuffle et al., U.S. Pat. No. 6,067,480; and Batchelder et al., U.S. Pat. No. 6,238,613; all of which are assigned to Stratasys, Inc., the assignee of the present invention. The modeling material may be supplied to the extrusion head in solid form, for example in the form of a flexible filament wound on a supply reel or in the form of a solid rod, as disclosed in Crump, U.S. Pat. No. 5,121,329. As described in Valavaara, U.S. Pat. No. 4,749,347, modeling material may alternatively be pumped in liquid form from a reservoir. In any case, the extrusion head extrudes molten modeling material from a nozzle onto a base. The extruded material is deposited layer-by-layer in areas defined from the CAD model. A solidifiable material which adheres to the previous layer with an adequate bond upon solidification is used as the modeling material. Thermoplastic materials have been found particularly suitable for these deposition modeling techniques.
Another layered-deposition technique for building models from a solidifiable material deposits droplets of modeling material from nozzles of a jetting head. Examples of apparatus and methods for making three-dimensional models by depositing layers of solidifiable modeling material from a jetting head are described, for example, in U.S. Pat. No. 5,136,515 to Helinski et al., and U.S. Pat. No. 6,193,923 to Leyden et al.
In creating three-dimensional objects by additive process techniques, such as by depositing layers of solidifiable material, it is the rule rather than the exception that supporting layers or structures must be used underneath overhanging portions or in cavities of objects under construction, which are not directly supported by the modeling material itself. For example, if the object is a model of the interior of a subterranean cave and the cave prototype is constructed from the floor towards the ceiling, then a stalactite will require a temporary support until the ceiling is completed. Support layers or structure may be required for other reasons as well, such as allowing the model to be removed from a base, resisting a tendency for the model to deform while partially completed, and resisting forces applied to a partially completed model by the construction process.
A support structure may be built utilizing the same deposition techniques and apparatus by which the modeling material is deposited. The apparatus, under appropriate software control, produces additional geometry acting as a support structure for the overhanging or free-space segments of the object being formed. Support material is deposited either from a separate dispensing head within the modeling apparatus, or by the same dispensing head that deposits modeling material. The support material is chosen so that it adheres to the modeling material. Anchoring the model to such support structures solves the problem of building the model, but creates the additional problem of removing the support structure from the finished model without causing damage to the model.
The problem of removing the support structure has been addressed by forming a weak, breakable bond between the model and the support structure, such as is described in Crump et al., U.S. Pat. No. 5,503,785. The '785 patent discloses a process by which a material that forms a weak, breakable bond with the modeling material is selected as either a support material or a release coating. Support material is deposited in layered fashion at the interface between the object and its support structure, or it is deposited in a layered fashion to form the support structure, in either case permitting the support structure to be broken away after formation of the object. When a release coating is used, it is deposited at the interface between the object and its support structure as a liquid, and forms a layer so thin that its geometry may be disregarded in the construction of the object.
In filament-fed Stratasys FDM™ three-dimensional modeling machines of the current art, a filament strand of the modeling material (or support material) is advanced by a pair of motor-driven feed rollers into a liquifier carried by the extrusion head. Inside the liquifier, the filament is heated to a flowable temperature. The liquifier is pressurized by the “pumping” of the strand of filament into the liquifier by the feed rollers. The strand of filament itself acts as a piston, creating a pump. As the feed rollers continue to advance filament into the extrusion head, the force of the incoming filament strand extrudes the flowable material out from the dispensing nozzle where it is deposited onto a substrate removably mounted to a build platform. Stratasys FDM™ three-dimensional modeling machines of the current art use as the modeling material an acrylonitrile-butadienestyrene (ABS) thermoplastic composition or a wax material. High-impact polystyrene has been used to create a break-away support structure. Additionally, Stratasys offers a material disclosed in pending U.S. patent application Ser. No. 10/019,160, sold under the name Waterworks™, for creating a soluble support structure.
An apparatus and method for layered deposition of high-strength engineering polymers to manufacture durable three-dimensional objects is disclosed in Stuffle et al., U.S. Pat. No. 6,067,480. Feed rods of the polymer are extruded from an extrusion cylinder using a piston which is displaced into the cylinder, providing high pressure extrusion accommodating of polymers having low melt flow and long chain lengths. The '480 patent discloses that feed rods of polycarbonate, polyaryletherketone and poly(methylmethacrylate) were successfully extruded using the extrusion cylinder apparatus. The '480 patent makes no disclosure of support materials.
Apparatus and methods for building three-dimensional models by layered deposition of high-temperature engineering thermoplastics are disclosed in pending U.S. patent application Ser. Nos. 09/804,401 and 10/018,673. These applications disclose the use of polycarbonates, polyetherimides, polyphenylsulfones, polysulfones, polyethersulfones and amorphous polyamides for building a three-dimensional model, but disclose no materials formulated for use in building a break-away support structure for such a model.
There is a continuing need to improve model strength and quality, by building models from high-performance engineering thermoplastics. Materials compatible with the modeling process are needed that will provide a suitable support structure for models built from high-performance materials.